"Heading Barehanded"... The Pride of Domestic Technology Made by Our Hands [Nuriho 2nd Launch]

[Asia Economy Reporter Kim Bong-su] The Nuri rocket, scheduled for its second launch on the 15th, is significant above all because it demonstrates the capability to launch our satellites using a launch vehicle developed with our own technology. In addition to the Korea Aerospace Research Institute (KARI), over 300 private companies participated to domestically produce all the technologies required for space launch vehicles from A to Z. The entire process?from design, manufacturing, testing, to launch?was completed with domestic technology. Although it was a challenging task akin to 'heading into uncharted territory,' we succeeded in developing the 75-ton class medium-to-large liquid rocket engine, clustering technology that combines multiple engines to produce the same thrust, large fuel and oxidizer tanks, engine test facilities, launch pads, and other development and operational infrastructure all with our own hands.

◇ No One Helped Us

Space launch vehicle technology can be diverted for weapons use, so international technology transfer is strictly prohibited under the Missile Technology Control Regime (MTCR) and U.S. export controls (ITAR). South Korea initially requested technology transfers from allies such as the United States but was reportedly turned away. While the U.S. transferred rocket technology to Japan in the 1980s, it heavily interfered with South Korea’s long-range launch vehicle development through missile guidelines until last year. South Korea was able to acquire Russian launch vehicle technology during the successful development of the Naro rocket in 2013, but even that was at a 'hearsay' level. Russia sold the first stage of the Naro rocket and received a large sum of money in exchange for manned space technology (astronaut training and International Space Station (ISS) experience), but kept the core technologies tightly hidden and did not transfer them. A representative case is Mr. Ko San, who was selected as an astronaut but was abruptly expelled in 2008 during training on grounds of confidential information leakage. A former official involved in cooperation with Russia said, "Russia showed our scientists their research and development facilities but did not provide proper explanations," adding, "They showed the process but probably thought, 'No matter how much we show, you won’t understand the secret.' Later, they were reportedly surprised to hear about our success."

Currently, only nine countries can independently launch space launch vehicles: Russia, the United States, Europe, China, Japan, India, Israel, Iran, and North Korea. However, among these, Israel, Iran, and North Korea are evaluated to have payload capacities of less than 300 kg. If the Nuri rocket succeeds, South Korea will secure a payload capacity of 1.5 tons, becoming the seventh country in the world capable of launching practical satellites weighing over 1 ton.

[Image source=Yonhap News]

◇ Independently Developed All Four Core Technologies

The flame temperature of the Nuri rocket exceeds 3,300 degrees Celsius. However, the blood and sweat of our engineers who completed the Nuri rocket with indigenous technology without external help were even hotter. First, developing the rocket engine to guarantee launch vehicle thrust was the top priority. Especially, the turbo pump, a core component, had to be manufactured, but no one had the knowledge, experience, or know-how. The turbo pump is an ultra-precision device that coordinates hundreds of valves down to 0.01-second intervals to supply fuel and oxidizer accurately. KARI researchers scoured classic textbooks from the U.S. and Russia and referred to old rockets in museums, igniting their passion. Led by those with experience in aircraft gas turbine engine development, they finally succeeded in development in 2008 after about five years of research. This was the result of overcoming difficulties such as explosions during the first experiment in 2007. At that time, KARI secured core component technologies for the rocket engine’s turbo pump, combustion chamber, and gas generator, which became the foundation for the 75-ton class liquid engine development for the Nuri rocket starting in 2010. The 75-ton engine development process was also full of challenges. As the engine size increased, combustion instability occurred, and after about six months of multiple design changes and experiments starting in 2017, the problem was barely resolved. Until just before the first launch last year, 33 prototypes were produced, and combustion tests were repeated 184 times for a total of 18,290 seconds.

Additionally, the 'clustering' technology, which combines multiple engines into one stage, was also developed independently. The first stage of the Nuri rocket bundles four 75-ton engines to produce thrust of about 300 tons, which is no easy feat. The engines must be precisely aligned and produce identical thrust for the rocket to fly along the intended trajectory. A KARI engine development official said, "Technologies such as flame heating analysis and insulation, thrust imbalance countermeasures, and assembly, alignment, and gimbaling (direction control) of four engines were necessary," adding, "Due to the high technical difficulty, precise design and high-level ground testing were required."

At first glance, manufacturing the propellant tanks seemed easy but was a complicated task. They had to be robustly made from thin special aluminum sheets 2-3 mm thick to withstand enormous internal and external pressures during launch. The Nuri rocket’s propellant tanks were designed to endure internal pressure six times atmospheric pressure and strong external forces generated by engine thrust and atmospheric resistance. Materials capable of withstanding the cryogenic temperature of minus 183 degrees Celsius of liquid oxygen, used as the oxidizer, were also used. The biggest challenge was to create huge structures 10 meters tall and 3 to 5 meters in diameter from such thin special materials. Across the first, second, and third stages of the Nuri rocket, there were over 2,000 points where the airtightness of the thin materials had to be inspected. KARI developed special welding technology independently and devised spinning techniques, completing propellant tanks that were leak-proof and sturdy through manual work. A KARI official said, "South Korea’s reputation as a 'world leader in welding technology in the shipbuilding industry' was actually a burden," adding, "Any mistake would mean repeating the 10-month manufacturing process, so extreme concentration and advanced technology were required."

[Image source=Yonhap News]

Another high-difficulty technology for space launch vehicles, the 'payload fairing,' was also a challenge but was successfully overcome. The payload fairing, a protective cover for the satellite, serves as a shield and must separate at the right time and with appropriate force upon reaching the target altitude. It requires lightweight and strong material technology and delicate know-how, which space powers keep highly confidential. KARI engineers made carbon composite fibers thin and then applied heat and pressure to achieve high strength, and also developed technology to mitigate separation shock (pyro shock) independently. After more than 200 experiments and repeated modifications, the technology was completed and its reliability was proven during the successful Naro rocket launch in 2013. In addition, engine test facilities capable of withstanding high heat and launch pads and operational systems equipped with advanced equipment were also successfully developed independently.

◇ The Jewel of Public-Private Space Technology Cooperation

From the development stage, the Nuri rocket aimed to foster a space launch vehicle industry ecosystem and strengthen industrial capabilities. Accordingly, technology cooperation and transfer took place in system final assembly, engine assembly, and manufacturing of various components. More than 300 companies actively participated, including about 30 leading firms. Notably, Korea Aerospace Industries (KAI) played a major role in hardware sectors such as system final assembly and tank and fuselage manufacturing. Hanwha Aerospace also took the lead in mechanical sectors of the launch vehicle, including engine final assembly, turbo pump, propulsion system supply system, piping, actuator systems, and thrust vector control system manufacturing and testing.

This content was produced with the assistance of AI translation services.